ilogb
, ilogbf
—get exponent of floating-point number#include <math.h> int ilogb(double val); int ilogbf(float val);
Description
All nonzero, normal numbers can be described as m *
2**p. ilogb
and ilogbf
examine the argument
val, and return p. The functions frexp
and
frexpf
are similar to ilogb
and ilogbf
, but also
return m.
Returns
ilogb
and ilogbf
return the power of two used to form the
floating-point argument.
If val is 0
, they return FP_ILOGB0
.
If val is infinite, they return INT_MAX
.
If val is NaN, they return FP_ILOGBNAN
.
(FP_ILOGB0
and FP_ILOGBNAN
are defined in math.h, but in turn are
defined as INT_MIN or INT_MAX from limits.h. The value of FP_ILOGB0 may be
either INT_MIN or -INT_MAX. The value of FP_ILOGBNAN may be either INT_MAX or
INT_MIN.)
Portability
C99, POSIX